This invention relates to a control stick, particularly for a helicopter, which can be rotatably positioned in three axes and has an electronic sensor for determining the control stick position.
It is known to use a non-contact inductive sensor arrangement to detect the rolling, pitching and yawing position of control sticks which can be adjusted in three axes. Such control sticks are used, for example, in fly-by-wire controlled blade angle adjusting systems of helicopters, and are usually equipped with an active stick force simulation. Such an arrangement is utilized in order to generate corresponding control commands for the blade angle adjustment and the stick force simulation. However, this arrangement requires a separate sensor and a separate signal processing for each control stick axis, so that the resulting sensor package requires undesirably high construction and weight expenditures and is difficult to accommodate under narrow installation conditions.
U.S. Pat. No. 3,432,671 discloses an opto-electronic position transmitter in which a rectangular light field is imaged by a deviation mirror which can be tilted in two axes, onto a sensor consisting of four photo cells arranged in a cross shape. The swivel position of the deviation mirror relative to the two axes of rotation is calculated, from the size of the illuminated surface parts. However, such a sensor is unsuitable for determining the position of a control stick, which can be adjusted in three axes. It also has the disadvantage of a limited measuring accuracy because external interfering influences, such as local fluctuations in the illumination intensity, distort the measuring result.
It is an object of the invention to provide a control stick of the initially mentioned type, which is constructionally simple, light weight and compact.
Another object is to provide such control stick which ensures extremely accurate and reliable measurement of the position of the control stick with respect to all three axes of movement.
According to the invention, this object is achieved by a special control stick sensor system having a double light beam which is swivelled in the same movement as the control stick. A detector surface, which is illuminated by the double beam along the whole adjusting range of the control stick, two-dimensionally scans the position of both light spots, and the control stick position is determined by signal analysis from the position coordinates of the two light spots.
The invention thus provides a constructionally simple, compact and light weight apparatus which uses a single sensor and an assigned electronic analyzing system to detect control stick movement according to size and direction, accurately and precisely in all three axes. The invention is therefore highly suitable for applications with strict weight limitations and narrow installation conditions, such as may exist, for example, in the helicopter construction.
In a further advantageous embodiment of the invention, one of the two light beams is aligned coaxially with respect to an axis of rotation of the control stick, so that a particularly simple, computation-related relationship is obtained between the position coordinates of the two light beam light spots on the detector mosaic and the rolling, pitching and yawing position of the control stick.
In order to save the light sensitive detector surface, the detector mosaic expediently consists of two detector fields which are separated from one another, and each of which is situated in the beam path of only one of the two light beams.
Moreover, for manufacturing reasons, the detector mosaic or the detector fields are preferably flat. The mutual position of the two light beams and optionally of the detector fields can be selected virtually arbitrarily according to the installation conditions. Thus, the two light beams may be inclined, and in particular may be aligned perpendicularly with respect to one another, which is recommended for a multiply redundant sensing system. However, generally, an essentially parallel mutual alignment of the two light beams is preferred.
In a constructionally particularly simple embodiment, the light beams are generated by two light-emitting diodes fastened to the control stick. However, it is also possible to provide a light-emitting single diode with a beam splitter arranged behind it to generate the double beam.
For sharp focussing of the light beams, focussed laser light may be used to form the light beams.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.